Was Jack just a figment of Rose's imagination in Titanic?

As part of part of our series on mind-blowing movie fan theories, we're changing the way you watch some of Hollywood's most famous films. This week: 'Titanic'.
 
The theory:
Given that it was the most successful movie ever made in its day, it's unsurprising there are boat-loads of fan theories regarding 'Titanic'. Some are patently ludicrous – Jack Dawson is a time-traveller; Jack Dawson is actually Jay Gatsby; Jack Dawson doesn't die but washes up on a beach, which is where 'Inception' begins – but there is one interesting theory which does, if you'll pardon the pun, hold a little water.
 
Yes, we put it to you that cheeky chappy Jack Dawson, with his impossibly chiselled cheekbones and his Joie de vivre spirit, was indeed too good to be true: he was merely a figment of Rose DeWitt Bukater's imagination as she suffered a psychotic episode aboard the Titanic at her lowest ebb.

The evidence:
- As we see from the movie's first half an hour or so, Rose is clearly not happy with her lot in life. She is being forced to marry a man she doesn't love, or even like, in order to save her family's fortune. It is quite possible that Rose is suffering from depression – she has been broken. It is only when she has run out of options and steps onto the ship's stern to kill herself that 'Jack' conveniently appears to convince her otherwise. "Come any closer and I'll jump!" she yells. "No you won't," says Jack, who is basically a voice in Rose's head – a manifestation of her fractured psyche, compelling her to hold on.
 
- Fiancé Cal is a douchebag of the highest order, so how convenient that the roguish young man who apparently saves her life is his polar opposite in every way? He's lower class as opposed to upper class, free-spirited instead of stuffy and takes risks where Cal prefers to stay the course. He's an artist not a businessman. He's kind to strangers, not rude and snobbish. In other words, he's imaginary and not real – a construct created by Rose to fill the void in her heart that Cal has left. The perfect man. Too good to be true.
 
- Seeing as the period story of Titanic's maiden voyage is being told by Old Rose aboard Bill Paxton's ship, that explains why we sometimes see Jack interact with other characters and follow his story i.e. the back-story Rose has invented for him. It is quite possible that Old Rose found the sinking of the Titanic so traumatic, she conjured up an imaginary lover to soften the blow.
 
- A lot of Jack's dialogue is very prescient for someone who's only just met her and enjoyed a steamy bunk-up with her in the back seat of a car. Lines such as "They've got you trapped, if you don't break free you're gonna die!" sound much more like Rose's conscience, don't you think? Consider Jack's parting lines: "Promise me you'll survive. That you won't give up, no matter what happens, no matter how hopeless. Promise me now, Rose, and never let go of that promise." This is essentially Rose convincing herself to stay alive.
 
- That famous shot of Rose at the bow of the Titanic? Notice the positioning of Jack and Rose – him standing behind her, supporting her, lifting her up. "I'm flying, Jack!" That's because 'Jack' represents Rose finally rediscovering her self-esteem and confidence.
 
- Then, of course, there's the most obvious piece of evidence of all: there were no records of any 'Jack Dawson' being on board the Titanic ("We never found anything on Jack... there's no record of him at all"). Responds Old Rose: "No, there wouldn't be, would there? And I've never spoken of him until now... But now you know there was a man named Jack Dawson and that he saved me in every way that a person can be saved. I don't even have a picture of him. He exists now... only in my memory." Uh-huh. We believe you, lady. (*cuckoo gesture*)

 
The verdict:
Any of you fancy raising this with James Cameron? Thought not. The director is famously meticulous with all of his movies and it's not likely that Cameron intended Jack to be seen as a figment of Rose's imagination – and there are certainly no overtly obvious suggestions that can be interpreted no other way.
 
However, the fact that almost the entire story is told from Old Rose's point of view does lend credence to theory that suggests she's an unreliable narrator, and many survivors of the Titanic understandably suffered massively from shock, which can do a strange thing to a person's memory. But then you could say the same about any film with a narrator who has undergone some trauma.
 
Now the 'Titanic'/'Inception' theory, that's really interesting...